• Alternatives

    synnoack • 12/12/2023 at 11:24 • 0 comments

    2.4GHz WiFi

    • Pros - Building wide coverage. Lots of bandwidth.
    • Cons - Mains power needed for most off-the-shelf low cost boards. Low power would need a custom build in all probability. Security is a concern unless upgrades to WiFi includes a segregated network for IoT devices.

    433MHz RTL-SDR Compatible

    • Pros - Many low cost temperature sensing remote units available. Operates for a very long time with AA batteries. Easy to integrate (e.g., OpenMQTTGateway).
    • Cons - Tests confirm that path loss is a big issue. Would need multiple receivers and they almost certainly need mains power.

    Zigbee

    • Pros - Many low cost temperature sensing remote units available. Operates for a very long time with AA batteries. Easy to integrate (e.g., Home Assistant). Mesh network can cover a lot of area with repeaters/routers.
    • Cons - Repeaters/routers need mains power. Potential interference from WiFi 2.4GHz radios disrupting transmissions.

    LoRa

    • Pros - Low power. Easy to integrate (e.g., OpenMQTTGateway). Very long range.
    • Cons - Limited Off-the-shelf hardware satisfying the low power requirement.

    All things being equal, Zigbee would be the best fit with the exception of the repeaters needing mains power. As a result, we are proceeding with LoRa as the wireless radio technology.

  • Requirements

    synnoack • 12/12/2023 at 11:22 • 0 comments

    General

    • Remote monitoring units send identity, temperature and battery level information
    • The frequency of data transmission must be configurable

    Ambient Temperature Monitoring Use Case

    • Remote monitoring units are able to operate on a single battery charge for at least 7 months (heating season)
    • Enclosed to prevent tampering but allowing room air flow
    • Temperature sensor within the enclosure
    • Indoor use (i.e., no need for weatherproofing) 

    Steam Trap Monitor Use Case

    • Two external temperature probes
    • Operate for at least 10 days on charge

  • Background Info

    synnoack • 12/12/2023 at 11:21 • 0 comments

    The origin of this project comes from a successful experiment to determine if it was possible to monitor water usage in the building having suffered a expensive leak that went unnoticed until the utility bill came. Using off-the shelf parts and software (rtlamr, RTL-SDR dongle, MQTT, InfluxDB, Grafana), we now have a close-to-real-time dashboard and alarming for anomalous events. In discussing some of the challenges of operating a steam heat system of this age, the current expert mentioned that if anyone notices this specific pipe being too hot to touch, we should call him to troubleshoot. That specific pipe was a steam condensate return line that should never be as hot as the steam supply line (~215 ℉). That condition is a symptom of one of the float and thermostat steam valves being stuck open which is simply a waste of energy. Our thought was that if we can monitor water usage, maybe we can monitor the temperature of that pipe. 

    We have a robust WiFi network throughout the buildings, so monitoring that condensate return and using WiFi to collect the data seemed to make sense. With an ESP8266 board, a DS18P20 temperature sensor, and a little ESPHomeYAML, the remote temperature monitor was created. We were able to get the MQTT messages with the temperature readings into the InfluxDB and create Grafana dashboards. The monitor was powered by a single 18650 LiPo cell because of a lack of mains power in the area where the return pipe is located. The ESP8266 board was not optimized for low power operation and monitoring ceased after about 10 days. We did discover a steam trap that was defective, so the monitoring experiment was a success. A second revision included two DS18P20 sensors to allow direct monitoring of the supply and return connections to a steam trap. The strategy being that a functioning trap should have a temperature delta between the supply and return. Most commonly these temperature deltas are checked with a IR Thermometer, but unless the heat zone is calling for heat, a novice might not be able to detect a real problem. The investigation of a more long lasting remote solution began. The scope was also expanded to monitor the ambient air temperature in all areas because only a few of the thermostats are connected so that the temperature can be pulled into a monitoring system. Knowing how adjustments or repairs impacted comfort levels seemed very important.

    One of the biggest challenges is the scale of the steam heat system, floor space involved, and the construction materials used. There are two not-so-recent natural gas fired low pressure steam boiler systems (one from the 1940's and the other 1960's vintage) which heat a three floor complex with a total combined floor space of 40,000 sq. ft. comprised of 46 rooms. The wide array of construction materials used in the various buildings is also a complication. Older portions are brick, concrete block or masonry. Path loss of the various wireless technologies in the environment is a major concern. An additional consideration is the availability of mains power for units. Since this is a multi-use building, it would be likely that a device would be randomly unplugged for some reason or that plugging something in permanently would not be allowed due to safety considerations.